The present invention relates to a method for continuous treatment of a textile product web with steam for fixing a reactive dye on natural fibers.
It also relates to a device for continuous treatment of textile product web of this type.
For fixing of reactive dyes on natural fibers, such as cotton or cellulose, it is known to first dry the moist product web on which the reactive dye is applied, and subsequently to fix the reactive dye on the fibers of the product web. For this purpose a promoter, for example urea, is needed and admixed to the reactive dye. The promoter holds the reactive dye in solution during dyeing and evaporates during fixing. This is true both for application of reactive dye on the product web by dyeing and also by printing.
For fixing of the reactive dye applied by printing, it is known to treat the dried product web with saturated steam. A suitable device with a steam chamber is disclosed in the patent document EP 0607 762B. For reduction of the urea consumption, this device is provided with a premoisturizing chamber.
A reduction of the urea quantity is possible, as described in the German patent document DE 43 03 129 02, in that the printed and dried product is sprayed with water immediately before its entry in the rapid festoon ager. This fixing process in the rapid festoon ager requires an average steam treatment time of 10-15 minutes. The product size generally amounts to 80-490 m, whereby a product speed of 5 to 50 in/mm results. In the rapid festoon ager the fixing of the reactive dye is performed conventionally with saturated steam at substantially atmospheric pressure, or in other words in saturated steam atmosphere. Rapid festoon ager for a product size of at least 80 meter is not efficient for smaller product sizes (smaller meter lengths).
A further appropriate steamer is disclosed in the German patent document DE 23 10 195 02. This steamer has a treatment chamber and a transporting device with at least partially horizontal product guidance by means of a conveyor. The treatment chamber is formed as a downwardly open hood. Thereby the entrained air can fall from a downwardly open steam space, so that a pure steam atmosphere is always available. Fixing of a drying product web in this steam atmosphere, in which a purely saturated steam atmosphere is also provided, is not possible without urea. The disadvantage of this steamer is that, due to the above mentioned steam treatment time of 10 to 15 min with saturated steam atmosphere in continuous operation, only small product speeds can be reached. Higher product speeds are possible only with greater structural length of the steamer with correspondingly higher investments and operation costs. The steam also is not efficiently usable when smaller quantities are to be dyed.
A further disadvantage of the above mentioned method is that the product web after application of reactive dye soluble in water is first dried and subsequently the reactive dye is fixed on the fibers. The both treatment stages of drying and fixing require two treatment devices. During pressing, conventionally for drying a pressing chamber and for fixing the above mentioned steam device are utilized.
In a special pressing method which is disclosed in the German patent document DE 196 33 101 the product web is moisturized, wet pressed and in wet condition evaporated without intermediate drying. The steaming is performed in a saturated steam atmosphere during 1.0-20 min at 96-105xc2x0 C. Also, in this method during use of a reactive dye for printing of cotton, urea in conventional quantity is utilized.
A further special pressing method in which the product web is first moisturized, the wet product web is printed and subsequently an evaporation-thermosol fixation process is performed, it is disclosed in the patent document WO96/28604. The evaporation-thermosol fixation process takes place with saturated steam at temperatures of 90, 150 and 170xc2x0 C. It requires a pressure-tight fixing device which conventionally is suitable only for a discontinuous operation.
Accordingly, it is an object of present invention to provide a method of continuous treatment of a textile product web with steam for fixing of reactor dye on natural fibers which avoids the disadvantages of the prior art and which is suitable for smaller meter lengths efficiently.
Accordingly, it is an object of present invention to provide a method of continuous treatment of a textile product web with steam for fixing of a reactive dye on a product web of natural fibers which avoids the disadvantages of the prior art and which is suitable and efficient for smaller meter lengths of the product web.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated in a method of treatment of a textile product web with steam for fixing of a reactive dye on a product web of natural fibers, which includes the steps of applying a reactive dye on a product web of natural fibers so as to form a moist product web with the reactive dye applied to it; subjecting a moist product web with the reactive dye on it to a steam treatment by bringing the moist product web with the reactive dye on it in contact with overheated water steam at a temperature of 130-230xc2x0 C.; transporting the moist product web during the foregoing steam treatment at least partially horizontally through at least one treatment chamber; and blowing the hot steam into the at least one treatment chamber onto the product web by nozzle boxes arranged above and below the product web.
In keeping with these objects another feature of present invention resides, briefly stated at least one treatment chamber, a transporting device having a horizontal conveyor guided through the at least one treatment chamber, a steam-tight housing which surrounds the at least one treatment chamber, the at least one treatment chamber being provided with at least one circulating device with at least one circulating fan and also with nozzle boxes arranged above and below the product web, the conveyor being formed as a sieve band.
When the method is performed and the device is designed in accordance with the present invention, the steam treatment can be performed effectively and thereby fast. Also, for fixing printed product webs are suitable.
In a method for continuous treatment of a textile product web with steam in which a moist product web of natural fibers with an applied reactive dye is brought in contact with steam, is subjected also to steam treatment, fixing treatment or dye fixing, with the steam, in accordance with the present invention in form of hot steam, or in other words overheated water steam at substantially atmospheric pressure. The hot steam is composed at least of 80 vol. %, preferably 95-100 vol. % (pure hot steam), of water steam. The hot steam has a temperature of 130-230xc2x0 C. in particular of 160-230xc2x0 C. In addition to the high product web temperature which with pure hot steam amounts to 100xc2x0 C., the additional temperature difference between the hot steam and the product web of 30xc2x0, in particular 60xc2x0 up to 130xc2x0 C. makes possible an acceleration of the reaction of the reactive dye with the natural fibers. This leads, when compared with a fixing treatment in saturated atmosphere to reduced heating and fixing time, and correspondently reduced retention time in a steamed treatment device and allows therefore devices which can be used efficiently for shorter meter length.
It is important that the inventive method uses overheated water steam for steam treatment so that the moist product web is dried during the steam treatment. It has been shown that drying the product during the fixing treatment leads to an acceleration reaction of the reactive dye with the natural fibers. This results in a further reduction of the fixing time.
In the steam treatment method for many reactive dyes it is also possible to eliminate use of urea. This is true for dyes of textile product webs in which the product webs dyed with reactive dyes have a moisture content of, for example, 40-80%. This is true also for the printing of textile product webs, in which the product webs printed with reactive dye have a moisture content of, for example, 10-40%.
In a surprising manner the steam treatment methods according to the invention with enhanced drying lead to good fixing results, namely to a high color yield and a good coloring quality corresponding to the result of the prior art.
In accordance with the present invention the product web during the steam treatment is transported at least partially horizontally through at least one treatment chamber. The horizontal product web guidance makes possible a fine transportation of the moist product web with the reactive dye applied on it. In contrast to this, in a roller conveyor steamer or in a rapid festoon ager due to the vertical product web guidance there is a danger of dye running. The horizontal product web guidance, which in the case of steam treatment with a saturated steam atmosphere requires large treatment chamber structural volumes for the given product size, is practical in connection with the efficient steam treatment according to the invention with overheated steam, also for smaller meter length web products
In accordance with the present invention, the overheated steam is blown onto the product web by nozzle boxes arranged above and below the product transport path in the treatment chamber. Preferably, the hot steam is guided in a circulating process. In contrast to the use of saturated steam atmosphere disclosed in the German patent document DE 23 10 195 02 without significant flow speed, the product web is blasted with overheated water steam. The blasting makes possible a higher exchange rate of the treatment steam on the outer surface of the product web and thereby a stronger energy supply per time than in a stationary steam atmosphere. By the blasting, the steam treatment is more efficient. The inventive steam treatment method is useful and improved for small meter length.
The utilization of overheated steam when compared with saturated steam during circulation through a circulating system has the advantage of a lower danger of condensation in the circulating system. With the use of the inventive method for printing of textile product webs, the moisture content of the printed product web before the steam treatment is adjusted to 10-40%, in particular 15-25%, and the product web is dried during the steam treatment to the residual moisture content of 1-10%, in particular 3-7%. In surprising manner, it has been determined that with the inventive method for a printed product web, optimal fixing results can be obtained with a residual moisture content of the product web smaller than the equilibrium moisture content. The equilibrium moisture content amounts, under normal conditions, to substantially 10% moisture, based on the weight of the product web, for cellulose and substantially 8% moisture for cotton. Regulation of the residual moisture content of the product web in the treatment chambers is not necessary.
The retention time of the product web in the treatment chamber can be 35-60 seconds, preferably 10-20 seconds. This retention time is sufficient for drying and for complete fixing with a good dye yield. It makes it possible to provide a treatment plant with comparatively small structural dimensions.
By the transportation of the product web by means of a sieve band, on the one hand a transportation of the product web through the treatment chamber can be performed without contact with the printed surfaces, and on the other hand a steam supply from above and from below on the product web is possible.
An arrangement for continuous treatment is also provided in accordance with the present invention. Since it has a steam-tight housing which surrounds all treatment chambers, the use of heat steam is possible. By means of the circulating devices with at least one circulating fan and nozzle boxes arranged above and below the product web, the steam treatment with hot steam is effective also with the fine, horizontal product web guidance.
The arrangement in accordance with the present invention is especially suitable for fixing of small meter lengths.
The transportation of the product web by a conveyor formed as a sieve band makes possible, with a contact-free transportation of the printed circuit of the product web, a steam supplied from above and below onto the product web. The device is therefore especially suitable for dye fixing of the printed product webs.
A great opening degree of the sieve band makes possible a great contact surface of the product web for hot steam. This leads to a high exchange rate and thereby to an efficient steam treatment. The deviating rollers for the conveyor formed as the sieve band arranged above the steam-tight housing simplified the construction of the arrangement. However, slots must be provided for entry and exit of the conveyor.
A return guidance of the conveyor under the housing requires only an in let slot and an outlet slot for the conveyor and makes possible an arrangement of a tensioning system and a drive for the conveyor outside of the steam-tight housing. This simplifies the construction of the arrangement. A guiding band can extend at an acute angle to a vertical through the inlet lock. It can be formed by the conveyor itself or a further band. It allows deviations of the product web by an angle of greater than 90xc2x0. Thereby the danger of negatively affecting the printing image by excessive deviations of the product web, such as in the case of a deviation around 90xc2x0, is reduced. The acute angle amounts to approximately 30-60xc2x0.
A supply band which extends in the vicinity of the conveyor running through the treatment chambers simplifies the supply of the starting portion of a new product web to the conveyor.
A supply band which extends through the inlet lock is especially suitable for devices with a conveyor running back through the treatment chamber.
In accordance with a further feature of present invention, locks are arranged before and after the housing. The locks extend from the bottom to over the transporting plane of the product web and are subdivided into a lower, downwardly open prechamber and a main chamber arranged over it. Suction passages or suction boxes can be connected with the prechamber. When compared with the known inlet and outlet slots with the suction boxes disclosed in the German patent document DE-A 195 46 344, due to the separate locks with the prechamber and aspiration device, the penetration of air and thereby condensation of steam to water is reliably prevented. A lock which is known from the German patent document DE 198 58 339, in which before the inlet slot of the housing steam is blown onto the product web, is less suitable for fixing of dye because of the danger of dye running.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.